Bernard, your comments regarding consultative reps are interesting. I agree that such folk can often have an influence on implementations of basic products. When, in a role of IT Quality Assurance Analyst, I attended a meeting discussing possible use of early touch screen monitors, our thoughts on use of such technology was indeed initially influenced by the reps. However, later, back at base, we considered things further and were mainly influenced by our own standards for implementation and usage, after which we did not buy into that technology.
When it comes to glassworkers using coloured enamels, I question whether the actual usage would have been influenced at all by any consultative representative, beyond confirmation of such things as working temperatures, coefficient of expansion etc.
As for comparisons of the way the enamels are worked in the Haden, Mullett & Haden examples, the Nazeing examples in Timberlake and the vase discussed here, I see no true similarity with the Haden, Mullett & Haden pieces. What I do see is a likeness in the "more cloudy style" of the vase discussed and the majority of the Nazeing equivalents in the book. For the H, M & H examples I see a "more delineated style" rather than "cloudiness" in the patterning. Even the blue vase on the right of Plate 31, page 50 in Timberlake, which has a "delineated" pattern still has "cloudiness" between the "delineated" parts.